JPH01108573A - Developing device - Google Patents

Abstract

PURPOSE:To prevent the toner from being dropped down to the outside of a developing device by providing a magnetic pole moving means for moving a magnetic pole positioned at the upstream side in the developer carrying direction from the tip part of an electrostatic latent image carrier side of the lower frame, to a position opposed to the tip part of the lower frame at the time of non-operation. CONSTITUTION:When a developing operation of an electrostatic latent image to an original image is ended, a solenoid SL is turned OFF and a magnetic roll 33 turns counterclockwise by an angle theta by restoring force of a spring 37c, and a developing main pole 33a moves to a position opposed to the tip part of a photosensitive drum 3 side of the lower frame 36. In this case, a magnetic brush of a high napping formed by the developing main pole 33a is brought into contact with the tip of the lower frame 36. Accordingly, a toner accumulated in the tip part of the lower frame 36 in the course of the developing operation is fetched into the developer of the magnetic brush formed by the developing main pole 33a. In such a way, even if vibration, etc., are applied, it does not occur that the toner drops down to the outside of a developing part from the tip part of the lower frame 36.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to an image forming apparatus using an electrophotographic copying process;
For example, the invention relates to a powder development type developing device used in copying machines, printers, and the like.

(Prior Art) Conventionally, this type of developing device includes a developing roller having a plurality of magnetic poles arranged along its inner circumferential surface, a toner supply means for supplying toner onto the outer circumferential surface of the developing roller, and It is equipped with a frame that covers the top and bottom of the roller, and develops an electrostatic latent image by rubbing a magnetic brush of developer made of toner and carrier formed on the developing roller against the electrostatic latent image carrier in the development area. be.

Then, the tip of the lower frame on the electrostatic latent image carrier side is separated from the developing roller to widen the opening, so that the developer on the developing roller flows from the development area to the portion facing the tip of the lower frame. Avoid interfering with the flow that passes between the developing roller and the lower frame, and scattering from the developing area.

The falling toner is caught and stopped at the tip of the lower frame.

(Problems to be Solved by the Invention) However, in the conventional developing device, toner that falls and accumulates on the tip of the lower frame during development may fall out of the developing device due to vibrations, shocks, etc. during non-development. There was a problem with the inside of the aircraft getting dirty.

For this reason, some large copying machines have a container below the tip of the lower frame to prevent the toner from falling, but if the container is full, it will overflow and the toner will still be used for development. It has the disadvantage that it can fall outside the device.

The present invention has been made in view of such problems, and an object of the present invention is to provide a developing device in which toner does not fall from the lower frame that covers the developing roller from below during non-developing time, and the inside of the device is kept clean. purpose.

(Means for Solving the Problems) In order to solve the above-mentioned problems, the present invention provides a developing roller in which a plurality of magnetic poles are arranged along the inner circumferential surface, and toner is supplied onto the outer circumferential surface of the developing roller. and a frame that covers the upper and lower sides of the developing roller, and the magnetic brush of the developer made of toner and carrier formed on the developing roller is rubbed against the electrostatic latent image carrier to form an electrostatic latent image. In a developing device for developing an electrostatic latent image carrier, the magnetic pole in the developing roller facing the electrostatic latent image carrier is formed to be movable in the circumferential direction of the developing roller, and when the magnetic pole is not in operation, the tip of the lower frame on the electrostatic latent image carrier side A magnetic pole moving means is provided for moving a magnetic pole located on the more upstream side in the developer transport direction to a position facing the tip of the lower frame.

(Function) In the above configuration, when the developing device is in operation, toner falls from the developer on the developing roller that has passed through the developing area onto the tip of the electrostatic latent image carrier side of the lower frame that covers the developing roller from below. accumulate.

When not in operation, the magnetic pole moving means moves the magnetic pole located upstream from the tip of the lower frame in the developer transport direction to a position facing the tip of the lower frame, thereby forming the magnetic pole. A tall magnetic brush on the developing roller contacts the tip of the lower frame.

Therefore, the space between the tip of the lower frame and the developing roller is blocked by the magnetic brush, and the toner accumulated on the tip of the lower frame during the above operation is taken into the developer of the magnetic brush and removed from the developing device. It will not fall.

(Example) Hereinafter, the present invention will be described with reference to the accompanying drawings showing one example thereof.

A. General Structure and Operation of Copying Machine FIG. 1 is a sectional view of a small-sized copying machine equipped with a developing device according to the present invention, and its structure will be explained together with its operation.

The main body of the copying machine (1) is equipped with an electrostatic latent material, which is made by depositing or coating selenium, zinc oxide, cadmium sulfide, or other organic photoconductors on the surface of a cylindrical body (for example, d30 mm) made of aluminum. Photosensitive drum (image carrier)
3) is located.

, this photosensitive drum (3) is rotated in the direction of arrow (a) by the drive of the main motor (2) based on the ON operation of a print switch (not shown), and the electrostatic charger (4) is rotated in the direction of arrow (a).
The surface is charged to a predetermined potential by the discharge.

In the optical system (8), an exposure lamp (9) is turned on, and the light is irradiated onto a document (not shown) placed on a document table (14) that scans in the direction of arrow (b), and the reflected light is The photoreceptor drum (3), which is charged to a predetermined potential as described above, is exposed to light from the exposure point (Xl) through the Selfox lens array (12), and the original image is formed on the surface of the photoreceptor drum (3). An electrostatic latent image corresponding to the image is formed. This electrostatic latent image is supplied with toner at a portion (X2) facing the developing device (5) and is visualized as a toner image. Note that this developing operation will be explained in detail later.

The copy paper (S) is transferred from the paper feed section (20) to the paper feed roller (21).
is fed one by one based on the rotation of the guide plate (22X
23), waits in front of the timing roller pair (24), and moves the transfer area (
X3), and the toner image is electrostatically transferred based on the discharge of the transfer charger (6).

The copy paper (S) onto which the toner image has been transferred is placed on the photosensitive drum (
After being separated from the surface of the copy paper (S), the toner image is transported by a transport belt (25) via a guide plate (26) to a fixing device (27), where the toner image is fused and fixed onto the copy paper (S). The paper is discharged onto the paper discharge tray (28).

After the residual toner on the surface of the photosensitive drum (3) that has passed through the transfer area (X3) is removed by a cleaning device (7), the light from the exposure lamp (9) passes through the opening (10) of the reflective shade (10). 11) and a mirror (13) to irradiate the region (x4) to remove residual charges.

B. Structure, etc. of the developing device (5) Next, the structure, etc. of the developing device (5) according to the present invention will be explained in the following order with reference to FIGS. 2 to 15.

1. Schematic configuration of developing device (5) i, developing section (30) stone, switching mechanism (41) iv, vibration mechanism (47) v, toner hopper (60X70) vi, opening/closing mechanism (80) vii, gap adjustment mechanism ( 90) Shaft, Lock mechanism (100) iX, Drive mechanism (120) Generally speaking, a first toner hopper (60) that accommodates black toner, a second toner hopper (70) that accommodates a color toner other than the color toner (for example, red toner), and the outer peripheral surface of the photoreceptor drum (3). The toner is selectively supplied from the toner hopper (60) or (70) and is formed on the surface of the photoreceptor drum (3). A developing section (30) supplies the electrostatic latent image.

i, Developing section (30X, see Figure 3.4) In the developing section (30), developing frames (31), (3
1) (one not shown) is the photosensitive drum support shaft (16)
It is rotatably attached to the back and front sides of the

The developing frames (31), (31) are equipped with a developing roller (32).
) is supported by a method described later, and a predetermined gap is formed between the developing roller (32) and the photosensitive drum (3).

Note that the developing roller (32) has an outer diameter of l16, for example.
A conductive, non-magnetic aluminum cylindrical body with a diameter of 1.5 mm and a micro-recess (depth 10 to 2002 m1) formed on the outer circumferential surface by blasting, etc., or a resin or oxide film formed on the surface of the aluminum cylindrical body. An insulating or semi-insulating material, or one in which an organic polymer film is plasma-polymerized on the surface of an aluminum cylinder by glow discharge in a vacuum is used.

Inside the developing roller (32), there are magnetic poles (33a) in the axial direction.
), (33b), (33c), and (33d) are arranged in the circumferential direction, and one end of the spindle is located inside the developing roller (32). The other end (34) of the support shaft protrudes from the developing roller (32) and the developing frame (31) and is rotatably supported by a bearing recess (not shown) formed in the developing roller (32) and the developing frame (31). On the other hand, the developing roller (32) has one end rotatably supported by the developing frame (31) and the other end rotatably supported by the spindle of the magnetic roller (33).

Therefore, even if the developing section (30) moves along the outer peripheral surface of the photoreceptor drum (3), the magnetic pole of the magnetic roller (40) maintains a constant positional relationship relative to the photoreceptor drum (3). be. That is, the magnetic pole facing the photosensitive drum (3) always faces the photosensitive drum (3).

Also, between the developing frames (31), there is an upper frame (31) that covers the upper and lower parts of the developing roller (32), respectively.
35) and the lower frame (36), and only the portion of the developing roller (32) facing the photosensitive drum (3) and the opposite side thereof are open. Then, lower frame (3
A stirring chamber (38) is formed along the axial direction on the surface facing the developing roller (32) of 6), and the inner surface of the stirring chamber (38) is a curved surface that allows the developer to flow smoothly without stagnation. The downstream side wall of the stirring chamber (38) in the developer conveying direction is a regulating portion (39) that faces the developing roller (32) with a predetermined gap therebetween.

As shown in FIG. 19, the magnetic roller (33) is movable by a magnetic pole moving mechanism (37). That is, the spindle (34) of the magnetic roller (33) is
It is driven by a solenoid (SL) via a lever (37a) and a link member (37b), and returned by a spring (37c).

First, during development, the solenoid (SL) is in the on state.
As shown in FIG. 18a, the main developing pole (33a) of the magnetic roller (33) is located on the line connecting the spindle (34) of the magnetic roller (33) and the spindle (I6) of the photosensitive drum (3). When the image is not being developed, the solenoid (SL) is turned off, and as shown in FIG. The pole (33a) is configured to stop at a position facing the tip of the lower frame (36) on the photosensitive drum (3) side.

Note that when the solenoid (SL) is turned on from the state shown in FIG. 18b to the developing state shown in FIG. 18a, the main developing pole (33a) of the magnetic roller (33) moves slowly. A damper mechanism may be provided.

Further, a developing section (30) is provided above and below the developing section (30), respectively.
The switches (Sl) and (S2) that detect this are installed.

As shown in Fig. 3, the developing section (30) having the above configuration is provided with the photosensitive drum (3), the charger (4), and the cleaning device (7) at the rear and front sides of these. The entire imaging unit (
The imaging unit (IU) is configured to be detachable from the copying machine main body (1).

The developing section (30) having the above configuration has a switching mechanism (41
), a vibration mechanism (47), etc. are attached, and these will be explained below.

■, Switching mechanism (41X, see Figure 4.5) Switching mechanism (41
) moves the developing section (30) along the outer peripheral surface of the photoreceptor drum (3), and changes the black development state (PI) and the color development state (
P2).

In this switching mechanism (41), a switching lever (42) is fixed to the developing frame (31) of the developing section (30),
A toner hopper (60) is attached to the switching lever (42).

A plate (43) located on the top surface of (70) is a lock. Further, a window (44) is formed in the plate (43), and the lever (42) is rotated in the direction of arrow (c).
When the developing roller (32) is switched to the black developing state (Pl) facing the supply roller (63) of the first toner hopper (60), the black mark provided on the upper surface of the toner hopper (60) is displayed in the window (44). (45) appears.

Conversely, by rotating the lever (42) in the direction of the arrow (C'), the developing roller (32) moves along an arc (Ll) with its center centered on the photoreceptor drum (3),
When switching to the color development state (P2) in which the developing roller (32) faces the supply roller (73) of the second toner hopper (70), the toner hopper (70) is placed in the window (44).
) so that the color mark (46) provided on the top surface appears.

Then, a black mark (45) or a color mark (46) appears through the window (44) on a display section (not shown) provided on the copying machine main body (1), and whether the copy is a silent image or a color developed copy is displayed. Displays whether it is possible.

iv. Vibration mechanism (see 47X Figure 6) The vibration mechanism (47) uses the switching mechanism (41) to switch the developing section (30) between the black development state (PI) and the color development state (PI).
P2) and the upper and lower frames (3).
5) and (36), thereby peeling off toner mechanically or electrically adhered to the inner surface of the frame.

This vibration mechanism (47) includes a spring vibrator (48),
(52) are each provided with a striking portion (50) on the photoreceptor drum (3) side.
), (54), is swingably supported by the upper frame (35) and lower frame (36) via fulcrums (49) and (53), and is supported in one direction by springs (51) and (55). is energized by In addition, the frame (57) provided with seven parts of the copying machine main body (1) has a support shaft (3) for the photoreceptor drum (3).
An uneven portion (56) is continuously formed on an arc centered at 16), and a vibrator (48) is located there.

The outer end of (52) is engaged.

Therefore, when the lever (42) of the switching mechanism (41) is held to switch the developing section (30) from the black developing state (Pi) to the color developing state (P2) or vice versa, the vibrator (48) ), (52) are repeatedly engaged with and released from the concavo-convex portion (56), causing the vibrators (48), (52) to vibrate, thereby causing the striking portions (50), (54) to move upward, respectively. The outer parts of the frame (35) and lower frame (36) are struck to give them vibration.

v, Toner hopper (60), (70X, see Figure 7)
The toner hoppers (60) and (70) supply black toner and color toner to the developing section (30), respectively.

These toner hoppers (60) and (70) are connected to the developing section (30).
) is removably located at the rear of the toner hopper (
At the front of the main bodies (61) and (71) of 60) and (70), there are supply rollers (63) in the openings (62) and (72).

(73) are arranged, and the respective supporting shafts (68) and (7g) are provided in the main bodies (61) and (71) with bearings (94) and (95).
X (see Figure 1O) is rotatably supported. Also,
The centers of the supply rollers (63) and (73) are located on an arc (L2) centered on the photoreceptor drum (3),
At a position where the outer peripheral surfaces of the supply rollers (63), (73) and the photosensitive drum (3) are closest to each other, the distance therebetween is slightly larger than the outer diameter of the developing roller (32).

Note that the supply rollers (63) and (73) have an outer diameter of -16 mm, for example, and have a depth of 10 to 200 mm by blasting, etching, or knurling on the outer peripheral surface.
A cylindrical body made of conductive, non-magnetic aluminum or the like is used, which has four microscopic parts of micrometers in size.

Also, the openings (62) of the toner hoppers (61), (71)
), (72) are provided with regulating blades (64), (74) and toner outflow prevention films (65), (75), the tips of which are attached to the rear outer peripheral surfaces of supply rollers (63), (73). are pressed into contact with each other.

The rear portions of the toner hoppers (60) and (70) are provided with the supply rollers (63) and (73), and the regulation blades (64) and (7).
4) and toner outflow prevention films (65) and (75) to form toner storage tanks (66) and (76), respectively, and toner storage tanks (6) of the first toner hopper (60).
6) rotatably accommodates a stirring blade (67).

Note that the switches (S 3 ) and (S 4 ) are switches that detect whether or not the toner storage tanks (60) and (70) are installed at predetermined positions, respectively, and their signals are output to a control device (not shown). It is now possible to do so.

vi, opening/closing mechanism (see 80X Figure 7.8) opening/closing mechanism (80X)
0) is the opening (6) of the toner hopper (60), (70).
2) and (72) are opened and closed to cut off the supply of toner from unused toner hoppers and prevent toner from falling.

This opening/closing mechanism (80) includes a supply roller support shaft (68),
Frame (81x81) on both ends of (78), (85)
(85) is rotatably supported, and the frame (85) is rotatably supported.
81X81) and (85X85) have opening/closing covers (8
2) and (86) are bridged.

The frames (81) and (85) are each integrally provided with segment gears (83) and (87), and are moved in the closing direction [arrow (d)] by springs (84) and (88).

(e) direction)]. The springs (84), (88) are wound around the support shafts (68), (78), one end is locked to the main body (61), (71), and the other end is connected to the frame (81), ( 85) respectively.

On the other hand, a segment gear (89) is integrally provided in the developing frame (31) of the developing section (30), and this segment gear (89) is connected to the segment gear (83) of the toner hopper (60), (70), (87) meshes with the developing section (
30) in the black development state (Pi) or color development state (P2).
), either one of the openings (62) or (72) is opened.

More specifically, when holding the lever (42) of the switching mechanism (41) and rotating the developing section (30) and the segment gear (89) in the direction of arrow (c) to set the black developing state (Pi), ( solid line state in Fig. 8), the segment gear (89)
segment gear (83) as it moves.

(87) rotate in the directions of arrows (d'') and (e), respectively, and as shown in FIG. is opened, and the opening (72) of the second toner hopper (7o) is closed with the opening/closing cover (86).

When holding the lever (42) and rotating the developing section (30) and the segment gear (89) in the direction of the arrow (C') to set the color developing state a (P2) (the state indicated by the two-dot chain line in Fig. 8),
Segment gears (83) and (87) are respectively indicated by arrows (d)
, (e') direction, and the first toner hopper (6
The opening (62) of the second toner hopper (70) is closed by the opening/closing cover (82), and the opening/closing cover (86) of the second toner hopper (70) is retracted to open the opening (72).

vi. Gap adjustment mechanism (90X, see Figures 9 and 10) The gap adjustment mechanism (90) adjusts the distance (gap) between the developing roller (32) and the opposing supply rollers (63) and (73) to a predetermined value. This is the value to be set.

In this gap adjustment mechanism (90), the developing roller (32
) has gap adjustment rollers (91) on both ends of the support shaft (33).
is rotatably provided. In addition, the supply roller support shaft (68
), (78) have gap adjustment rollers (92) at both ends, respectively.
, (93) are rotatably provided.

On the other hand, the supply roller bearings (94) and (95) formed on the side walls of the toner hopper bodies (61) and (71) have a slightly larger diameter than the supply roller support shafts (68) and (78). A gap is formed between (68), (78) and the bearing (94), (95).

Further, stoppers (, 96), (97) are formed on the side walls of the toner hopper bodies (61), (71), and between the stoppers (96), (97) and the support shafts (68), (78). springs (98) and (99) are interposed, and the support shaft (
68) and (78) are biased toward the developing section (30) in the direction of the arrow.

According to the gap adjustment mechanism (9o) having the above configuration, as shown in FIG. (6o) Gap adjustment roller (92
) are pressed into contact with each other, and the developing roller (32) and the supply roller (63
) A predetermined gap is set between the two.

When the developing roller (32) is switched to the color developing state (P2), the gap adjustment roller (91) of the developing roller (32)
) is the second toner hopper (70) gap adjustment roller (
93), and a predetermined gap is set between the developing roller (32) and the supply roller (63).

vIi+, locking mechanism (see 100X figures 11-13)
The locking mechanism (100) locks the first toner hopper (60) when the developing section (3o) is in the silent image state a (Pi), and locks the second toner hopper (60) when the developing section (3o) is in the color developing state (P2). (70).

In this lock i configuration (100), the developing frame (31)
Lock release parts (101) and (102) are provided on the outer surface of the release part (101), and the surface of the release part (101) [the surface facing the stopper (103) described below] slopes upward in the direction of arrow (C). The surface of the release portion (102) [the surface facing the stopper (104)] slopes upward in the direction of the arrow (C'').

On the other hand, as shown in FIG. 12.13, the copying machine main body (1) is provided with stoppers (lO3) and (104) located on the sides of the toner hoppers (60) and (70), respectively. The rear part of the is fixed to the copying machine main body (1) via fixing members (105) and (106), and stoppers (103) and (l
O4) (7) Free end niha, retaining hole (107), (10
8) are formed respectively. Also, toner hopper (60)
, (70) have supply rollers (
63), coaxially with (73), said body 1t, (107)
, (108) and approximately the same diameter (f) engaging protrusion (IO9), (
l l O) is formed.

In the locking mechanism (100) having the above configuration, the 11th
As shown in the figure, the developing frame (31
) is set to the black development state (Pi), the release section (
102) slips into the tip of the stopper (104), the retaining hole (108) of the stopper (104) is released from the engagement protrusion (l l O) of the second toner hopper (70), and the toner hopper ( 70) is removable (see FIG. 13). On the other hand, as shown in FIG. 12, the stopper (103) of the first toner hopper (60) has its tip connected to the developer 7
Press the side surface of the frame (31) and insert the retaining hole (l O7).
is engaged with the engagement protrusion (109), and the first toner hopper (
60) is locked in a non-removable state.

Hold the lever (42) of the switching mechanism (41) and turn on the developing section (3).
0) to the color development state (P2), the release part (101) sinks into the surface facing the stopper (103) and the first toner hopper (60) is set in a removable state, contrary to the above. and the release part (102) is pressed against the stopper (
The second toner hopper (7) is evacuated from the opposite part of the
0) is locked.

That is, when the developing section (30) is in the black developing state (Pl), the first
The second toner hopper (60) is locked and cannot be taken out, and only the second toner hopper (70) is set to be removable. Conversely, the developing section (30) is in a color developing state (
At the time of P2), the second toner hopper (70) cannot be taken out, and only the first toner hopper (60) is set to be removable.

ix, drive mechanism (120X, see Figure 14.15) In the drive mechanism (120), the support shaft (1
The photosensitive drum drive gear (121) provided in 6) is drivingly connected to the main motor (2) (see Figure 1), and the developing roller drive gear (122) attached to the spindle of the developing roller (32). is adapted to rotate around the photoreceptor drum drive gear (121) while meshing with it via the developing frame (31), and these gears (121) and (12
2) constitutes a differential gear device.

Also, the support shaft (68) of the supply rollers (63) and (73).

Supply roller drive gears (124) and (126) are attached to (78) via a supply roller drive clutch (clutch corresponding to supply roller (73) 127X is not shown), and these supply roller drive gears (124), (1
26) mesh with idler gears (123) and (125), respectively.

Further, although not shown, the stirring blade (67) provided in the first toner hopper (60) is connected to the supply roller drive gear (12).
4) so as to rotate together with the supply roller (63). Note that the stirring blade (67) may be connected to the drive system of the document table (14) so that it rotates as the document table moves.

In the drive mechanism (120) having the above configuration, the developing section (
30) is set to the black developing state (PL), as shown in FIG. It meshes with the gear (123).

Therefore, when the main motor (2) is driven in this state and the photosensitive drum drive gear (121) rotates in the direction of the arrow, the developing roller drive gear (122), idler gear (123), and supply roller drive gear ( 124)
rotate in the directions of the arrows, and the photosensitive drum (3) and the developing roller (32) rotate in the directions of the arrows, respectively. Further, when the supply roller drive clutch (127) is turned on by a signal from a control device (not shown), the supply roller drive gear (127) is turned on.
24) is transmitted to the supply roller (63).

When the developing section (30) is switched from the black developing state (Pi) to the color developing state (P2), the developing roller drive gear (12
'2) moves along the circumference of the photoconductor drum drive gear (121) while meshing with it, and moves to the second toner hopper (70).
The idler gear (125) meshes with the idler gear (125).

Therefore, when the main motor (2) is driven in this state and the photosensitive drum drive gear (121) rotates in the direction of the arrow, the developing roller drive gear (122) rotates in the direction of the arrow.
), idler gear (125), and supply roller drive gear (126) each rotate in the direction of the arrow, and the photoreceptor drum (
3) The developing rollers (32) rotate in the directions of the arrows.

Further, when a supply roller drive clutch (not shown) is turned on, rotation of the supply roller drive gear (126) is transmitted to the supply roller (73).

x,) toner density control means (see Figure 2) Next, the developing section (
30) The density adjustment means for the toner supplied will be explained.

A developing bias voltage (vb) is applied to the developing roller (32) of the developing section (30), and the supply rollers (63) and (73)
) has a DC bias (V ss) and an AC bias (Vr
A recovery bias voltage (Vs) is applied in which the voltages (mS) are connected in series, and the bias voltages (Vb) and (Vss) are variable, and by adjusting the voltage value, the toner concentration on the developing roller (32) is adjusted. It is possible.

xi, developer In the developing device (5) having the above configuration, a two-component developer consisting of toner and carrier is used.

As the carrier, a binder type carrier having a particle size of 20 to 100 μm, a ferrite carrier, an iron powder carrier, or a carrier whose surface is overcoated with an appropriate resin is used, and the carrier is a developing roller (32).
The magnetic roller (40) is magnetically held on the outer peripheral portion of the magnetic roller (40).

The toner used has a particle size of 5 to 30 μm and is manufactured by a pulverization method or suspension polymerization method, or a capsule toner. As mentioned above, the first toner hopper (60) contains black toner. The second toner hopper (70) contains color toner (for example, red toner).
is accommodated.

A necessary and sufficient amount of developer is supplied around the developing roller (32) so that it can be restrained by the magnet of the magnetic roller (33) in the developing sleeve (32). That is, the developer around the developing roller (32) is held by the magnetic binding force of the internal magnetic force, and the amount of developer is such that it will not shift or slip even if the developing device is tilted.

Therefore, all the developer around the developing roller (32) is
As the developing roller (32) rotates, it circulates without stagnation. Therefore, during toner collection, which will be described later, all of the toner in the developer is removed and collected, improving toner collection efficiency. In addition, the developing section (30) requires
In addition, since only a sufficient amount of developer is present and the amount of developer is set small, toner removal and supply are performed in a short time, reducing toner replacement (color change) time. Moreover, the developing device becomes more compact, and the process unit becomes smaller.

C1 Black Developing Operation The thermal developing operation using black toner in the first toner hopper (60) will be described below.

The developing section (30) is set to the thermal developing state (Pl) by the switching mechanism (41), and a black mark (see 45X Figure 4) is displayed on the display section (not shown) of the copying machine body (1). is displayed, the developing roller (32) is opposed to the supply roller (63) of the first toner hopper (60), and the developing roller (32) is opposed to the supply roller (63) of the first toner hopper (60).
As shown in figure b, when the solenoid (SL) is off,
It is assumed that the developing main body (33a) of the magnetic roller (33) is located at a position facing the tip of the lower frame (36) on the photosensitive drum (3) side.

On the other hand, it is assumed that the gap adjustment mechanism (100) and the like are set as described below.

That is, in the gap adjustment mechanism (90), as shown in FIG. 9, a predetermined gap is established between the developing roller (32) and the supply roller (63) by pressure contact between the gap adjustment rollers (91) and (92). is retained.

In the opening/closing mechanism (80), as shown in FIG. 7, the opening/closing cover (82) of the first toner hopper (60)
2), and in the second toner hopper (70), the opening (72) is closed by the opening/closing cover (86). Therefore, color toner does not fall from the second toner hopper (70) in such a state.

In the locking mechanism (100), as shown in FIG. 11, the first toner hopper (60) is locked in a non-removable state, and the second toner hopper (70) is set in a removable state.

In the drive mechanism (120), as shown in FIG. 15, the developing roller drive gear (122) is connected to the first toner hopper (60
), and the rotational force of the photoreceptor drum drive gear (121) is applied to the developing roller drive gear (
122), an idler gear (123), and a supply roller drive gear (124).

In the toner density adjustment means, the developing bias voltage (Vb),
A recovery bias voltage (Vss) is set in each developing state.

When the print switch is turned on with each part of the developing device (5) set as described above, the solenoid (SL) shown in FIG. 19 is turned on and the magnetic roller (33) rotates clockwise in the figure. As shown in FIG. 18a, the main developing pole (33a) of the magnetic roller (33) aligns with the spindle (34) of the magnetic roller (33) and the spindle (34) of the photoreceptor drum (3). I6), that is, the position on the line connecting photoreceptor drum (3
) and becomes ready for development. As shown in FIG. 2, based on the drive of the main motor (2), the photosensitive drum (3), the developing roller (32),
The stirring blades (67) rotate, and the supply roller (63) rotates based on the ON operation of the supply roller drive clutch (127).

As a result, in the toner storage tank (66), the stirring blade (6
Based on the rotation of step 7), the black toner is conveyed forward while being mixed and stirred, and at this time, toner blocking and crosslinking phenomena are prevented.

At the outer periphery of the supply roller (63) facing the toner storage tank (66), as shown in FIG. and the excess material is scraped off at the tip contact portion of the regulating blade (64).

The toner taken into the minute recesses is removed by the regulation blade (64
), the toner is frictionally charged to a positive polarity by contact with the regulating blade (64), and a thin layer of charged toner is formed on the surface of the supply roller.

On the surface of the developing roller (32), as shown in FIG.
When the carrier is conveyed in a magnetic brush state along the lines of magnetic force generated by the magnet of the magnetic roller (33), and the toner thin layer is conveyed to the opposing portion between the supply roller (63) and the developing roller (32). , on the surface of the developing roller (32) based on the scraping action of the brush-like carrier and the difference between the bias voltages (Vb) and (Vs) applied to the developing roller (32) and the supply roller (63). Black toner is supplied.

Here, in the area where the developing roller (32) and the supply roller (63) face each other, not only the above-mentioned toner supply operation but also
In parallel, a collection operation is also performed to collect excess toner from the carrier on the developing roller (32) to the supply roller (63).

The toner supplied to the surface of the developing roller (32) is conveyed in the direction of the arrow based on the rotation of the developing roller (32).
First, the two are mixed on the circumferential surface of the developing roller. Next, the developer is transported to the stirring chamber (38), where it is further mixed well and charged to a predetermined value, and then moved to the regulating section (39).
The surface of the developing roller (32) that has passed through the opposing part is coated with toner and carrier at a predetermined ratio (toner concentration: 6 to low).
The two-component developer mixed with t%) is adjusted and set to a developable state.

In this state, the electrostatic latent image formed on the surface of the photoreceptor drum (3) is conveyed to the part facing the developing roller (32), and the two-component developer is applied to this electrostatic latent image. It is rubbed and visualized as a black toner image.

The toner that scatters and falls from the developer trying to leave the photoreceptor drum (3) is removed from the lower frame (36).
A receiver is fixed at the tip of the photoreceptor drum (3) side, and the particles are deposited there.

The developer that has passed through the part facing the photoreceptor drum (3) is chopped at the part facing the regulating member (39) and most of it falls into the stirring chamber (38). The developer is mixed with the developer mixed in the direction of the arrow while forming a vortex, erasing the toner consumption pattern during development, and some of the developer is again held on the surface of the developing roller (32) and supplied. It is transported to the opposite part of the row 5C63),
At this point, toner is supplied again. In addition, the stirring chamber (38)
The inner surface of the developing roller (33) is a smooth curved surface and is formed within the range of the magnetic binding force of the magnetic roller (33), so the developer does not stay in one place and the rotation of the developing roller (32) It is constantly mixed and stirred.

The toner collected by the supply roller (63) is conveyed in the direction of the arrow based on its rotation, passes through the contact portion of the toner outflow prevention film (65), and is collected into the toner supply tank (66).

When the electrostatic latent image development operation for the document image is completed in this way, the solenoid (SL) shown in FIG. 19 is turned off based on a signal from the control device (not shown) during the auto-shut time of the copying machine. Due to the return force of the magnetic roller (33) and spring (37c), as shown in Fig. 18b,
The developing main pole (33a) is rotated counterclockwise in the figure by an angle θ.
moves to a position opposite to the tip of the lower frame (36) on the photosensitive drum (3) side.

At this time, as shown in FIG. 18b, the main developing pole (33a)
The magnetic brush with high ears formed by the lower frame (36
). Therefore, the toner accumulated on the tip of the lower frame (36) during the developing operation is
It is taken into the developer of the magnetic brush formed by the main developing pole (33a). Therefore, even if vibrations etc. are applied in this state, toner will flow from the tip of the lower frame (36) to the developing section (
30) It will not fall outside.

Then, the developing bias voltage (vb) and/or recovery bias (Vs) are switched from the developing state to the standby state,
A portion of the toner from the surface of the developing roller (32) is collected into the toner storage tank (66), and the toner concentration on the developing roller (32) is set to 0-1-2.0 wt%.

D. Development unit switching operation Next, from the black development state (Pl) to the color development state (P2
), as shown in Fig. 4, hold the switching lever (42) and rotate the developing section (30) in the direction of the arrow (C''). (not shown) is displayed with a color mark (46).Furthermore, the vibration mechanism (47) and the like described below are operated as follows.

In the vibration mechanism (47) shown in FIG. 6, a vibrator (48),
The tips of (52) sequentially engage with the uneven portions (56) of the frame (57), and the striking portions (5) of each vibrator (48), (52)
0) and (54) are electrically and mechanically attached to the surfaces of the upper frame (35) and lower frame (36) by continuously hitting the upper frame (35) and lower frame (36), respectively. The black toner that is attached will be peeled off.

In the gap adjustment mechanism (90) shown in FIGS. 9 and 10, the gap adjustment roller (91) of the developing roller (32)
The supply roller (63) is separated from the gap adjustment roller (92) of the toner hopper (60), and is biased by a spring (98) to move slightly in the biasing direction.

Further, when the developing section (30) is switched to the color developing state (P2), the gap adjustment roller (9) of the developing section (30)
1) is pressed against the gap adjustment roller (93) of the second toner hopper (70), and the gap adjustment roller (93) moves slightly in the direction opposite to the arrow direction against the biasing force of the spring (99). The developing roller (32) and supply roller (7)
3), a predetermined gap is uniformly formed along the axial direction.

In the opening/closing mechanism (80) shown in FIGS. 7 and 8, the developing section (30
), the segment gear (89) moves in the direction of the arrow (C'
) direction, the toner hopper (6
The segment gears (83) and (87) of the first toner hopper (60) rotate in the directions of arrows (d) and (e'), respectively, and the opening (62) of the first toner hopper (60) opens with the opening/closing cover (
82), and the opening (72) of the second toner hopper (70) is opened when the opening/closing cover (86) is retracted therefrom. Therefore, in this state, black toner does not fall from the first toner hopper (60).

In the locking mechanism (100) shown in FIG. 11.12, as the developing frame (31) moves, the release part (101) slips into the opposite surface of the stopper (103), and the other release part (102) (104), the first toner hopper (60) is set in a removable state, and the second toner hopper (70) is locked in a non-removable state.

In the drive mechanism (120) shown in FIG. 14.15, the developing roller drive gear (122) moves as the developing section (30) moves.
The second toner hopper (70
), and the rotational force of the photoreceptor drum drive gear (121) is transmitted to the developing roller drive gear (125).
122) to the idler gear (125) of the second toner hopper (70) and the supply roller drive gear (126).
It is set to a state where it can be transmitted.

During the above developing section switching operation, the developing section (30)
rotates around the photoreceptor drum (3), and the vibration mechanism (47) etc. operates, applying vibrations, shocks, etc. to the lower frame (36), and there is a concern that toner may fall from the tip thereof. . However, as described above, when the thermal development operation is completed, the main developer pole (33a) is in a position facing the tip of the lower frame (36), and the magnetic brush formed by the main developer pole is in the lower frame (36). The toner that is in contact with the tip of the lower frame (36) and has fallen and accumulated on the tip of the lower frame (36) is held by the magnetic brush.
Toner does not fall out of the developing section (30) during the switching operation.

E. Black toner removal operation As described above, the developing section (30) is in the black developing state (Pl)
When the state is switched to the color development state (P2) and this is detected by the switch (S2), the solenoid (SL) shown in FIG. 19 is turned on and the main development pole (33a) is , as shown in FIG. 18a, moves to the closest position to the photosensitive drum (3) and becomes ready for development. Then, the main motor (2) operates, and the 14th
The photosensitive drum drive gear (
121), the developing roller drive gear (122), and the supply roller drive gear (124) start rotating, and the photoreceptor drum (3) starts rotating based on the discharge of the charging charger (4).
) is uniformly charged.

At this time, the supply roller drive clutch (not shown) attached to the support shaft (78) of the supply roller (73) of the second toner hopper (70) is turned off, and the supply roller drive gear (126) is turned off. ) is rotated by the supply roller (73
) will not be transmitted.

Then, when switching the black toner remaining in the carrier held on the surface of the developing roller (32) and the developing section (30) from the black developing state (Pl) to the color developing state (P2), the vibration mechanism The black toner peeled off from the upper frame (35) and lower frame (36) based on the impact action of (50) is conveyed along the outer periphery of the developing roller (32) based on the rotation of the developing roller (32), and is transferred to the photosensitive drum (3). The developing roller (32) is electrostatically supplied to the surface of the developing roller (32).
Black toner is removed from the outer periphery.

The black toner thus supplied to the surface of the photoreceptor drum (3) is conveyed in the direction of arrow (a) based on the rotation of the photoreceptor drum (3) and collected by the cleaning device (7). Note that in order to increase the toner recovery efficiency, a developing bias voltage having the same polarity as that of the toner may be applied to the developing roller (32).

When the black toner removing operation described above continues for a predetermined period of time and almost all of the black toner is removed from the peripheral surface of the developing roller (32), color development becomes possible.

As a result, black toner is not supplied to the electrostatic latent image during color development, and image quality does not deteriorate due to color mixing or the like.

When the toner removal operation is completed, the solenoid (SL) shown in FIG. 19 is turned off and the main developing pole (33a) is switched to the first
As shown in FIG. 8b, the toner is moved to a portion opposite to the tip of the lower frame (36) to prevent the toner from falling from the lower frame (36).

The above-described toner removal operation is performed when the copying machine is powered on, after power outage or jam removal, and even after toner hopper replacement, and toner is removed from the developing section (30).

Note that the toner removal operation after turning on the power of the copying machine is performed during the warming-up time of the fixing device (27), the temperature control time,
It is carried out during the leveling time of the applied oil.

F. Color development operation With the development device (5) set as described above,
When a print switch (not shown) is turned on, the solenoid (SL) shown in FIG. 19 is turned on based on a signal from a control device (not shown), and the main developing pole (33a) is turned on.
As shown in FIG. 18a, the photoreceptor drum (3) moves to the closest position and becomes ready for color development.
The developing bias (vb) and recovery bias voltage (Vs) are set to the developing state again.

Next, the photosensitive drum (3) rotates in the direction of the arrow (a) based on the drive of the main motor (2), and the developing roller (32) in the developing device (5) rotates in the direction of the arrow, and the supply roller is driven. A clutch (not shown) is turned on. As a result, in the second toner hopper (70), a thin layer of color toner is formed on the outer peripheral surface of the supply roller (73), and the color toner is supplied to the surface of the developing roller (32). A two-component developer of a predetermined concentration consisting of carrier and color toner is adjusted at the outer peripheral portion.

Generally, the amount of charge of color toner is lower than that of black toner, and in order to achieve the brightness unique to colors such as red and blue, it is necessary to make the image density darker than black, so the color toner is adjusted here. The density is higher (8 to 10 wt%) than the black toner density (about 5 wt%) during the thermal development operation.
%) set.

The surface of the photoreceptor drum (3) is equipped with a charger (
After being charged by the discharge in step 4), an electrostatic latent image is formed based on the image exposure from the optical system (8), and this electrostatic latent image is supplied with color toner at a portion opposite the developing roller (32). The image is visualized as a color toner image.

When the above developing operation is completed, in the developing device (5), the solenoid (S L) shown in FIG. 19 is turned off, and the main developing pole (33a) is again connected to the lower frame (36 ) to prevent the toner from falling from the lower frame (36). In addition, the developing bias voltage (Vb) and the recovery bias voltage (Vs)
is switched to the standby state, and the toner density on the surface of the developing roller (32) is in the standby state (toner density 20.1 to 2.2.
Owt%).

Further, when the developing section (30) is switched from the color developing state (P2) to the black developing state (Pl), the black developing state (Pl)
1) to the color development state (P2), the upper frame (35) and lower frame (35)
The color toner adhering to 6) is peeled off and the developing section (
When the switch (sl) detects that the developing roller (30) has been switched to the black developing state (PI), the developing roller (32)
starts driving, and the remaining color toner is supplied to the surface of the photoreceptor drum (3) and collected by the cleaning device (7), and most of the color toner is present on the outer periphery of the developing roller (32). It is set to not.

Therefore, the next time a silent image is performed, no color toner will appear on the image.

In addition, as shown in FIG. 16, the cleaning device (7)
The toner collection section (170) includes a toner collection pipe (17).
1) is connected, and its tip is connected to the supply roller (63) or (
The supply roller (63) or (73) is rotatably connected to the toner collection section (170) and the toner collection pipe (171) via a bearing structure (not shown).
) is provided with a conveyance coil (172) having one end fixed to a support shaft (175) of a cleaning device drive gear (174) that meshes with the photoreceptor drum drive gear (121). Further, another transport coil (173) is fixed inside the supply port (63) or (73).

Therefore, the toner collected by the cleaning device (7) is transferred from the toner collecting section (170) to the supply roller (63) or (73) via the toner collecting pipe (171) based on the rotation of the conveying coil (172). transported inside. The toner conveyed to the supply roller (63) or (73) is
Fixed conveyor coil (173) and supply roller (63)
Or, based on the rotation of (73), the supply roller (63) or (73) is gradually stored from the back side.

In the embodiment described above, switching of the developing section (30) was performed by manually operating the switching lever (42).
As shown in FIG. 17, a solenoid (SL) may be provided in the copying machine main body (1), and the switching lever (42) may be operated by turning it on and off. The switching lever (42) is always biased by a spring (sp) in a direction opposite to the operating direction of the solenoid (SL).

Here, if the solenoid (SL) is turned off after a certain period of time has passed after color toner development, the switching lever (42) will be pulled back by the spring (SP) and the developing section (
30) returns to the black development state (Pi).

In this way, by configuring the device to return to a state in which development with black toner is possible after a certain period of time after completion of development with color toner, that is, a state in which it is frequently used, even if color development has been performed previously, However, it is guaranteed that a black copy can be obtained immediately without any color change operation, eliminating the trouble of color change, eliminating copy mistakes, and making copies more efficient.

Further, in the above embodiment, the lower frame (36) is made of a non-magnetic material, but if its tip is made of a magnetic material, the main developing pole (33a) can be made of a magnetic material, as shown in FIG. 20a. When moving to the tip of the lower frame (36a), the tip of the lower frame (36a) becomes magnetized and attracts the tip of the magnetic brush.
A magnetic brush is formed in a bridged state between a) and the developing roller (32).

Therefore, this cross-linked magnetic brush is connected to the developing roller (3).
2) and the lower frame (36),
Toner is prevented from falling on the lower frame (36).

When the main developing pole (33a) returns to the closest position to the photoreceptor drum (3), as shown in FIG. However, if the cross-linked state collapses and the carrier is separated, the lower frame tip (36a), which is a magnetic material, will become less magnetized, so the carrier in this residual developer may remain on the developer. Magnetic pole (33a) with toner
Or the developing roller (32) based on the magnetic force of the magnetic pole (33b)
It is attracted by the upper magnetic brush and incorporated into the developer.

Therefore, the toner deposited on the lower frame (36a) during previous development is completely wiped away.

Further, in the above embodiment, the magnetic pole moving mechanism (37) is used to move the main developing pole (33a) of the magnetic roller (33) to the tip of the lower frame (36). This is because the main developing pole (33a) is the closest to the lower frame (36) among the magnetic poles located upstream in the developer transport direction.

Therefore, in a developing device in which another magnetic pole exists between the main developing pole and the tip of the lower frame, the other magnetic pole may be moved to the tip of the lower frame instead of the main developing pole.

Further, in the above embodiment, the developing device is configured to switch to a toner hopper containing toner of a different color by rotating the single developing roller (32) around the photoreceptor drum (3) with a constant gear pump. The present invention is applied to, but is not limited to this type of device, it is not limited to a device in which a plurality of toner supply means containing toners of different colors are arranged around a single developing roller in a fixed state, or As shown in Japanese Unexamined Patent Publication No. 61-201271, a plurality of toner supply means are arranged around a rotating shaft, and by rotating the rotating shaft, one of the toner supply means is made to face the developing roller. It can also be applied to things that have been

Furthermore, the present invention can be applied not only to developing devices capable of changing colors as described above, but also to preventing toner from falling in ordinary developing devices.

(Effects of the Invention) As is clear from the above description, according to the present invention, the magnetic pole moving means moves the tip of the electrostatic latent image carrier side of the lower frame that covers the developing roller from below and the developing roller during non-operation. Since the space between the developing device and the developing device is blocked by a magnetic brush, the toner accumulated on the tip of the lower frame during operation is prevented from falling outside the developing device, and the inside of the developing device is not contaminated with toner when it is not in operation. It has the effect of keeping it clean.
/Xru.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing a schematic configuration of a copying machine equipped with a developing device according to the present invention, FIG. 2 is a cross-sectional view of the main part of FIG. 1, FIG. Figure 4 is a perspective view of the switching mechanism, Figure 5 is a sectional view showing the movement of the developing roller, and Figure 6 is a perspective view of the switching mechanism.
Figure 7 is a cross-sectional view of the vibration mechanism, Figure 7 is a cross-sectional view of the toner hopper, Figure 8 is a side view of the opening/closing mechanism, Figures 9 and 10 are side views of the gear/knob adjustment mechanism, and Figure 11 is a side view of the locking mechanism. figure,
FIG. 12 is a sectional view showing the locked state of the locking mechanism,
Figure 3 is a sectional view showing the unlocked state of the locking mechanism;
4 is an exploded perspective view of the drive mechanism, FIG. 15 is a side view showing the switching state of the drive mechanism, FIG. 16 is a sectional view of the toner collection mechanism, and FIG. 17 is a perspective view showing another embodiment of the switching mechanism. , FIGS. 18a and 18b are cross-sectional views showing the states of the magnetic roller during operation and non-operation, respectively. FIG. 19 is a side view of the magnetic pole moving mechanism, and FIGS. 20a and 20b show other embodiments. FIG. 4 is a cross-sectional view showing the state of toner at the tip of the lower seven frames during non-operation and operation, respectively. 3... Photosensitive drum (electrostatic latent image carrier), 5... Developing device, 32... Developing roller, 33... Magnetic roller,
37... Magnetic pole moving mechanism, 60. 70... Toner hopper (toner supply means) 63. 73... Supply roller (toner supply means) Patent applicant Minolta Camera Co., Ltd. agent Patent attorney Seihaku Ao and 2 others

Claims (1)

[Claims] (1) A developing roller having a plurality of magnetic poles arranged along an inner circumferential surface, a toner supply means for supplying toner onto the outer circumferential surface of the developing roller, and a frame covering the upper and lower sides of the developing roller; In a developing device that develops an electrostatic latent image by rubbing a magnetic brush of a developer made of toner and carrier formed on a roller against an electrostatic latent image carrier, The magnetic pole is formed to be movable in the circumferential direction of the developing roller, and when not in operation, the magnetic pole located upstream in the developer transport direction from the tip of the lower frame on the electrostatic latent image carrier side is moved to the tip of the lower frame. 1. A developing device comprising a magnetic pole moving means for moving the magnetic pole to a position facing the developing device.